Endocrine System Flashcards
1
Q
what was the first experiment on hormones? what was the conclusion from this study?
A
Berthold, 1849 - examined a rooster under three conditions
1. control - grows up like a normal rooster
2. remove testicles - grows up more like a hen
3. remove testicles and re-implant testicle from another animal into the abdomen - grows up like a normal rooster
- we concluded that the testicles release some sort of chemical messenger that travels through the blood to reach its targets
- testes make a “secretory blood-borne chemical”
- when group 2 animals grew up, implanting a testicle made no significant difference
- suggests hormones have organizational (appearance) and activational (behavioural) effects
2
Q
how and where are hormones released?
A
- released primarily by glands (but also other tissues)
- released primarly into the bloodstream (but also locally)
- released primarily by animals (but also plants)
exocrine glands - release fluids outside the body
endocrine glands - release hormones inside of the body
3
Q
what are some cells that secrete chemicals into the bloodstream?
A
- neurocrine - neural communication, when neurons release neurotransmitters
-
endocrine - release hormones into the blood stream to get to the target
- can’t target specific cells like neurons
-
autocrine - cells that release a signal to themselves
- create a negative feedback loop to reduce the amount of neurotransmitter released
- paracrine - chemical message is released to cells that are close, strongest affects are on closest cells
- pheromone - within species communication through secretion of a hormone outside the body
- allomone - different species communicating through secretion of a hormone outside the body
4
Q
what are the principles of hormone function?
A
- slow acting, gradual effects
- effect could take hours or weeks after the hormone enters the blood stream
- changes the probability or intensity of behaviours changes but not whether they happen or not
- behaviour and hormone release are reciprocal
- hormone secretion happens in bursts or pulses at specific times each day or each month
- hormones can interact and can create unique effects that neither hormone can do on their own
- hormones need receptors in order to have their effect
5
Q
what is multiplicity of action in hormones?
A
- multiplicity of action - the same hormone can affect different target tissues in different ways
- this is based on what the hormone is binding to
6
Q
what does the hypothalamus do? what types of cells does it have?
A
- hypothalamus is the main junction between the nervous and endocrine systems
- hypothalamus contains neuroendocrine cells (neurosecretory cells)
- look like neurons, but they synapse onto the blood stream
- same chemical message but travelling in different ways
- some hormones are also neurotransmitter
- ex. epinephrine and norepinephrine
7
Q
what are the different types of hormones?
A
- peptides, amines, and steroids
- peptides and amines are also neurotransmitter categories
- amines are small, like amino acids
- peptides are the large category of neurotransmitters
- they are long strings of amino acids
8
Q
how do different types of hormones get across the cell membrane?
A
- amines and peptides are mostly stuck outside of the cells
- some amines have the ability to cross the plasma membrane
- steroid hormones are especially good at crossing the plasma membrane
- structure is similar to cholesterol
9
Q
what are the different types of hormone receptor types?
A
at the membrane (for all three types)
- GCPRs, G-protein coupled receptors
- work faster
- they are on the plasma membrane, so they are useful for amines and peptides
- don’t have to have all receptors at the membrane since some hormones can travel through the membrane
intracellular - for steroids and some amines
- steroid receptors are inside the cell
- work much slower
- usually near the nucleus
- these receptors are transcription factors (change the expression of genes)
- can have GCPRs as well
10
Q
what are methods in measuring hormones and receptor types?
A
radioimmunoassay, autoradiography, immunohistochemistry/immunocytochemistry, in situ hybridization
11
Q
what is radioimmunoassay?
A
-
radioimmunoassay - used to measure hormone levels in the blood
- take blood sample and increasingly add antibodies that bind to the hormone
- tells us the amount of the hormone in the blood
12
Q
what is autoradiography?
A
-
autoradiography - used to look for brain area affected by the hormone
- inject a radioactive hormone and watch it bind to targets
- put photo paper onto the slice, radioactive parts are shown on the paper
- shows where hormone receptors are in the brain
13
Q
what are immunohistochemistry and immunocytochemistry?
A
- used to look for brain area affected by the hormone
- create an antibody for the hormone receptor
- shows where the receptors are, similar to autoradiography
- immunohistochemistry - looking at a section of tissue
- immunocytochemistry - looking at levels of cells growing in a petri dish
14
Q
what is in situ hybridization?
A
- shows us where the hormone receptor RNA is and when more hormone receptor RNA is expressed
- take a complementary strand of DNA or RNA and add a fluorescent tag to it
- shows us activation of transcription or which cells have the protein itself
- the protein - hormone receptor RNA
15
Q
what are the negative feedback mechanisms for hormones?
A
autocrine feedback, target cell feedback, brain regulation, brain and pituitary regulation
16
Q
what is autocrine feedback?
A
- hormone is released and makes it to target cell, but some will bind to receptors on the endocrine cell that released it
- causes an inhibitory effect
17
Q
what is target cell feedback?
A
- releasing hormone results in a change in the intensity or probability of behaviours (biological response)
- biological response changes hormone release from endocrine cells
18
Q
what is brain regulation (negative feedback mechanism)?
A
- releasing hormone results in a change in the intensity or probability of behaviours (biological response)
- biological response changes activity in the hypothalamus
- change in hypothalamus affects endocrine cells that release hormones
19
Q
what is the pituitary gland?
A
- the other side of the nervous system/endocrine intersection
- nervous system side - hypothalamus, which affects the pituitary gland
- endocrine side - pituitary gland
- the infundibulum connects the hypothalamus and pituitary
- the pituitary has anterior and posterior divisions that play separate roles
- they originate from different tissues and release different hormones
20
Q
what is the posterior pituitary?
A
- no dedicated endocrine cells in the posterior, just axons from the hypothalamus
- hypothalamus has neuroendocrine cells in paraventricular and supraoptic nuclei
- axons travel down infundibulum to capillaries in the posterior pituitary (median eminence)
- these hypothalamus axons terminate on capillaries
21
Q
what hormones does the posterior pituitary release?
A
- axons from hypothalamus neuroendocrine cells that are in the post. pituitary release oxytocin and vasopressin/anti-diuretic hormone (ADH) into blood
-
oxytocin: stimulate uterine contractions in pregnancy; milk letdown reflex (ejects milk from milk ducts)
- can be learned by the sound of baby’s crying
-
ADH: reduces urination to conserves water when dehydrated or have too much sodium
- also blood vessel constriction
-
oxytocin: stimulate uterine contractions in pregnancy; milk letdown reflex (ejects milk from milk ducts)
22
Q
how does alcohol impact ADH and dehydration?
A
- alcohol inhibits L-type calcium channels, which inhibits ADH release (which usually reduces urination)
- alcohol makes you urinate more and makes you more dehydrated
23
Q
what is the anterior pituitary? how does it relate to the hypothalamus?
A
- there are dedicated endocrine cells that release hormones
- hypothalamus release releasing hormones, that trigger activity in the anterior pituitary
- releasing hormones carried (only a few mm) via hypophyseal portal veins
- when releasing hormones arrive, anterior pituitary cells release tropic hormones
- this controls the release of many other hormones
- tropic hormones travel to glands and cause further hormone release
- anterior pituitary has its own hormone-producing cells
24
Q
what is the process of hormone activation?
A
Releasing hormones (HTh) → tropic hormones (anterior pituitary gland) → hormones (gland) → target
25
what is the corticotropin releasing hormone? what tropic hormone does it lead to? what is the tropic hormone's main target?
- corticotropin releasing hormone released from neuroendocrine cells of the hypothalamus
- causes adrenocortico tropic hormone (ATH) to be released, whose main target is the adrenal cortex
- adrenal cortex releases corticosteroids
- related to stress, circadian rhythms, arousal
26
what is the thyrotropin releasing hormone? what tropic hormone does it lead to? what is the tropic hormone's main target?
- thyrotropin releasing hormone released from neuroendocrine cells of the hypothalamus
- causes thyroid-stimulating hormone to be released, whose main target is the thyroid
- thyroid releases thyroid hormones
- related to changes in metabolism
27
what are the gonadotropin releasing/inhibiting hormones? what tropic hormone do they lead to? what is the tropic hormone's main target?
- gonadotropin releasing/inhibiting hormones released from neuroendocrine cells of the hypothalamus
- cause lutenizing hormone/follicle-stimulating hormone to be released, whose main target is the gonads (testes/ovaries)
- gonads release/don't release androgens or estrogen/progestin hormones
28
what is the prolactin releasing peptide/prolactin inhibiting factor ? what tropic hormone does it lead to? what is the tropic hormone's main target?
- prolactin releasing peptide/prolactin inhibiting factor (dopamine) released from neuroendocrine cells of the hypothalamus
- cause prolactin to be released, whose main target is the mammary glands
- causes milk production, also related to parental behaviour
29
what are somatocrinin and somastatin? what tropic hormone does it lead to? what is the tropic hormone's main target?
- somatocrinin (stimulates) or somastatin (inhibits) released from neuroendocrine cells of the hypothalamus
- cause growth hormone to be released, whose main target is bones
30
what are the 6 main tropic hormones?
1. adrenocortico-tropic hormone
2. thyroid-stimulating hormone
3. lutenizing hormone
4. folicle-stimulating hormone
5. prolactin
6. growth hormone
31
what is the adrenal gland composed of?
- **adrenal cortex** - outer layer, is 80%
- gets input from anterior pituitary
- **adrenal medulla** - inner layer, is 20%
- gets inputs from autonomic nervous system, sympathetic nervous system
- adrenal cortex releases **steroid hormones**
32
what hormones does the adrenal cortex release?
adrenal cortex releases **steroid hormones**
- **glucocorticoids (cortisol)** - related to stress and circadian rhythms, increase blood glucose and breakdown of proteins
- **mineralocorticoids (aldosterone)** - causes salt and water retention
- **sex steroids (androstenedione)** - influence body hair patterns for male vs. females
- synthesized on demand via Adrenocorticotropic Hormone because steroids easily move past blood brain barrier and so they can’t be floating around all the time
33
what hormones does the adrenal medulla release?
- adrenal medulla releases **amine hormones** (catecholamines)
- epinephrine
- norepinephrine
34
what hormones does the thyroid gland release? what is their role?
- releases thyroid hormones, **thyroxine and triiodothyronine** and calcitonin
- they are amines but act like steroids
- can cross through the membranes but are amines
- have intracellular receptors as well as receptors on the membrane
- generally regulate growth and metabolism, also an general activating affect on the nervous system
35
what does the thyroid gland require?
- only place in the body that requires iodine
- this is why we are recommended to eat iodized table salt
- lack of iodine leads to hypothyroidism
36
what is the pineal gland? what does it release? what is the function?
- not a target of the pituitary, unlike the adrenal and thyroid
- some call it a third eye (eye type spot on some animals) has photo receptors to measure days and seasons, not conscious sight
- releases melatonin in relation to the amount of light we are exposed
- more is released at night
- receives inputs from sympathetic nervous system
37
how does melatonin affect animals?
- since it can help measure seasons, there is a relationship between melatonin release and the gonads in some animals
- as melatonin release goes up, gonadotropin releasing hormones go down
- which means that in dark seasons, there is lots of melatonin release, which shrinks the gonads of some animals
38
what are the gonads? what is the process of hormone release?
- there are two compartments in male and female gonads
1. for sex hormone production
2. for gamete production
- hypothalamus released GnRH or GnIH →
- anterior pituitary release FSH and LH →
- which cause changes to the gonads
- kisspeptin stimulates GnRH, especially released in the onset of puberty
39
for both the testes and ovaries, what are the parts for sex hormone production and for gamete production?
Testes
- sertoli cells produce sperm
- leydig cells create androgens (testosterone)
Ovaries
- ova are mature gametes
- steroid hormones (progestins)
40
what do hormones mainly effect?
hormones are important in determining our appearance and projection of development (puberty)
41
what is an example of how behaviour can influence hormones?
- **psychosocial dwarfism** - isolation from parents or neglect (high levels of stress in childhood) inhibits growth hormone released
- when removed from the stressful environment, develop returns to normal
42
why is it hard to tell if hormones are determining behaviour?
- cortex supersedes many older controls for behaviour
- makes it harder to determine the aspects of behaviour affected by hormones
- most vigorous responses are observed in animal models
- behaviour also influences hormones
43
what happens when we give rats an injection of oxytocin?
exogenous oxytocin in rats - rats spend more time touching each other
44
what is the ventral pallidum? how does it relate to oxytocin and vasopressin?
- ventral pallidum - main target of the nucleus accumbens and is related to motivation and socialization
- prairie voles are monogamous animals
- the females have a high density of oxytocin receptors in the ventral pallidum
- the males have a high density of vasopressin receptors in the ventral pallidum
- meadow voles are a similar species, but are not monogamous
- both males and females have lower densities of oxytocin and vasopressin receptors
- high oxytocin and vasopressin receptor density in the ventral pallidum is associated with monogamous behavior and social bonding
45
what happens when we remove the gene for oxytocin in rats?
oxytocin knock-outs in mice - rats display social amnesia, don’t recognize mice that they’ve met before
46
is oxytocin the love molecule?
- no, the story of oxytocin as a love molecule is more complicated than we thought
- we have helped social anxiety of mice by blocking oxytocin receptors
- blocking oxytocin makes them more social when they’re stressed out
- there is a relationship between people’s childhood history, cocaine addiction, and oxytocin
47
how has oxytocin been seen to increase group biases?
- people injected with oxytocin were less likely to sacrifice a member of their in-group in the trolley problem
- also more likely to sacrifice a member outside of the group
- only builds “love” towards people who they already have a bias towards
48
how has oxytocin been seen to increase a propensity for revenge?
- in groups where revenge is activated, their levels of oxytocin in their saliva is higher
- increasing the likelihood of revenge also relates to higher levels of oxytocin release
49
do pheromones actually influence behaviour?
- pheromones are chemical messages that are released that elicit hormonal changes in other individuals within the same species
- in non-human animals, pheromones do affect behaviour via the **vomeronasal organ (VNO)**
- they have unique receptors to the olfactory organ
- in humans, there is a VNO but its related genes for pheromone receptors are basically non-existent
50
in what ways have we seen that pheromones influence behaviour in humans?
- putative human pheromone effects often don’t replicate
- **McClintock’s effect** - women’s menstrual cycles sync up over time
- **men’s sweat** - samples of men’s armpit sweat was taken and women were asked to smell it, and were asked to rate the smells
- rated some smells higher than others, those that belong to people who had a complimentary immune system
51
what is the dual pathway for stress?
1. **HPA axis** - hypothalamus → anterior pituitary → adrenal cortex (releases cortisol)
2. **sympathetic nervous system** - adrenal medulla releases norepinephrine and epinephrine
52
how does the hippocampus affect the HPA axis?
- when we are resilient, the hippocampus inhibits the HPA axis, it provides negative feedback to the hypothalamus
- under chronic stress conditions, the hippocampus is damaged, dendrites diminish, it shrinks
- less negative feedback on the hypothalamus, more stress
53
what study showed that we interpret the stress response and give it meaning?
- **schacter and singer** - gave participants a “new vitamin” (epinephrine), and put them in a room with someone else
- the other person in the room was either joyful or grumpy
- the person in the room with the grumpy person interpreted the stress as annoyance
- the person in the room with the joyful person interpreted the stress as happiness
